Countryside Corner Neighborly Garden News

Issue 67, November 2017

Are native cultivars as good for pollinators as native species?

There has been a growing demand for native plant material to address pollinator decline in the United States. Creating pollinator friendly landscapes has been promoted as having ecological benefits, and good for our environment. Consequently, this has led to the selection and breeding of native cultivars. A native cultivar or ‘nativar’ is a cultivated variety of a native plant that has been cross-bred and/or hybridized by plant breeders seeking certain desirable traits. The flowers of nativars may vary from native species by the size, shape, color, abundance and bloom time. These attributes are known to affect pollinator behavior; how and when pollinators will visit the flowers. Nativars are also bred and selected for disease resistance and more garden friendly sizes; which could make them more desirable landscape plants.

However, when humans choose traits they find attractive, such as double flowers or unusual colors, these traits may be less alluring to pollinators, and actually decrease the quantity, quality, and accessibility of the plant’s nectar and pollen. Generally, only native species are used in land restoration projects, however nativars are widely used in the landscape industry; it is actually hard to find true native species at local garden centers, it is almost impossible to find a non-cultivated variety of Echinacea purpurea these days.

With agencies like the ‘National Pollinator Garden Network’, and ‘Pollinator Health Task Force’ working to register and improve millions of acres of land and pollinator gardens, it is crucial that we investigate how nativars compare to native species. Do they perform the same ecological functions in pollinator habitats? Annie S. White, doctoral student of Plant and Soil Science at the University of Vermont, has been studying this topic since 2011. Under the guidance of Dr. Leonard Perry, she established identical experimental pollinator gardens in northern Vermont locations (zones 4a and 4b). Ms. White has been studying pollinator visitation to 12 native species, and 14 nativars, evaluating garden performance, and nectar production.

One very strong trend was observed across all species evaluated; the more manipulated the cultivars became, the less attractive they were to pollinators. Nativars that were the result of many repeated breeding selections had significantly fewer visits from pollinators. However, some nativars attracted as many, or more pollinators than the species. These were typically those varieties that were selected from open pollinated seed nativars such as: Asclepias tuberosa ‘Hello Yellow’.

Asclepias tuberosa ‘Hello Yellow’

The nativar Veronicastrum virginicum ‘Lavendelturm’ (aka ‘Lavender Towers’) unexpectedly attracted many more pollinators than the native species, and actually performed better as well. The results strengthen the idea that there is potential to select and market those varieties that have more appeal to our pollinators.

which is pollinated by hummingbirds, has been hybridized and also crossed with the native Lobelia siphilitca (which is bumble bee pollinated). The resulting plants have beautiful flowers, but offer decreased volumes of nectar, and nectar sugars than the unhybridized species. These plants will grow well, and be very showy in the garden, but the pollinators will be rewarded with 20% less of the nectar energy than they would receive from the native species, according to Ms. White. Results may vary regionally, but the research done by Ms. White shows that pollinators, and particularly bees, show strong preferences for native species of flowers. She suggests limiting nativar use in pollinator gardens to those that are open-pollinated and seed grown. Cultivars that differ significantly in color and appearance from the native species, should be used only sparingly, and those cultivars derived from crosses of two species should be avoided for use in pollinator habitat restoration.

November’s ‘to-do’ list

Keep watering woody plants until the ground freezes. We have had very dry conditions through the fall, and this can have a negative impact on the health of our trees and shrubs. Evergreens, especially, need to go into winter well hydrated to avoid winter injury, caused by desiccation. Newly planted evergreens may benefit from a timely application of an anti-desiccant type spray, to help minimize winter drying.

There is still time to transplant deciduous trees and shrubs; as long as the ground remains unfrozen, and weather permits. Their roots will continue to grow even though they’ve dropped their leaves. Be sure to water them regularly, and mulch the roots well to retain moisture.

Target areas where rodents and moles might congregate and do damage over the winter. Remove any heavy buildup of fallen plants and wet matted down leaves, attractive places for them to hide. If you’ve had severe rodent damage previously, you may have to put out traps or baits to reduce the population. Protect young, and thin barked tree species with hardware cloth secured around the lower trunk. This will help stop rodents from gnawing, and thus ‘girdling’ trees. When trees are girdled, bark has been mostly or completely removed around the entirety of the trunk, and can kill the tree.

Prune out any rampant suckers from your lilacs. These take away energy needed to put out flowers. Suckers are the vigorous shoots that emerge from the base of the plant. Leave any major pruning until next year, after the lilacs bloom.

If you’d like to plant aliving Christmas tree this year, dig a hole now before the ground freezes, and mulch the hole with straw covered with a tarp to keep the soil workable.

Finish clearing out gutters before it snows. Clogged gutters create ice dams later in the winter; which may lead to leaks and roof damage.

Most houseplants will be going dormant now. Reduce your plants watering schedule, and skip fertilizing them until new growth begins again in the spring. However, their need for humidity is still greater than most home environments. Lack of humidity also creates optimal conditions for mealy bugs and scale insects. I usually mist my orchids daily in the winter, and grow them on pebble filled trays. My fall and winter blooming orchids are in active growth, and actually require more work now than in the summer.

Hang out suet feeders to encourage insectivorous birds to keep scouring your garden for bugs. They will continue to hunt for insects, just beginning to hide for the winter, throughout your beds. Consider adding bird friendly shrubs for food and shelter throughout the seasons to your garden. Even if you feed birds, they still need a place to fly back to quickly; to escape from predators. Sparrow hawks in particular love to swoop down on bird feeders and snatch away unsuspecting birds.

Clean up all dropped fruit and other debris from beneath your fruit trees. Pests and diseases can overwinter in the plant matter, ready to re-infest your trees next spring.

Now that roses are dormant, prune them back to 18” and use mulch to cover the bud union to 6” deep. Protect the canes with a rose cone, or tie the canes together and wrap them with burlap.

Need help getting your home and yard ready for the holidays? Countryside Landscape can help with outdoor and indoor decorating; wreaths, Balsam roping, trees and lights.

Winter is a good time for pruning; sap loss is minimal, causing less stress to the plant. The risk of infection by plant pathogenic fungi & insects will be minimized too, as they are dormant now. When the leaves are off deciduous trees and shrubs, you get a better view of the true shape of the plant.

To begin, make sure your pruning tools are clean & sharp. Tree branches grow from stems at nodes & pruning always takes place on the branch side of a stem-branch node. Branches and stems are separated by a thin piece of tissue called a stem collar which grows out from the stem at the base of the branch. All cuts should be made on the branch side of the stem collar. This protects the stem, & other branches growing from it, and allows the plant to heal cleanly.

Performing the 3-cut method illustrated, helps ensure a clean cut without tearing the bark. To help minimize stress, do not take off more than 25% of the crown in a pruning session.

Thinking ahead…

Do you feed birds through the winter? Try planting trees and shrubs to provide a living winter food source for our feathered friends. Birds also need a protected area to roost, and shelter from storms.

Ilex verticillata-Winter-berry Holly is an outstanding native plant. This deciduous holly bears bright red berries, very attractive to birds, and great for Christmas decorating. There is also an orange fruited variety. Grows 3-8’ tall, depending on the cultivar.

Picea-The Spruce family are stately conifers, which offer tasty cones for seed eating birds. There are native as well as non-native species available as nursery trees. Spruce also provide necessary shelter from winter storms and a place to roost. Most Spruce are full sized trees, growing 40-60’ tall.

Picea glauca

Picea glauca cones

Juniperus virginiana-Eastern Red Cedar and its cultivars bear firm berries that persist throughout the year; ready for hungry birds. A handsome native tree or shrub; Junipers are excellent for creating a sheltered area for birds. There are many cultivars to choose from, grows from 3-40’ tall.